// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/base/audio_pull_fifo.h"

#include <algorithm>

#include "base/logging.h"
#include "media/base/audio_bus.h"

#undef min
#undef max

namespace media {

AudioPullFifo::AudioPullFifo(int channels, int frames, const ReadCB& read_cb)
    : read_cb_(read_cb)
    , fifo_(AudioBus::Create(channels, frames))
    , fifo_index_(frames)
{
}

AudioPullFifo::~AudioPullFifo() { }

void AudioPullFifo::Consume(AudioBus* destination, int frames_to_consume)
{
    DCHECK_LE(frames_to_consume, destination->frames());

    int remaining_frames_to_provide = frames_to_consume;

    // Try to fulfill the request using what's available in the FIFO.
    int frames_read = ReadFromFifo(destination, remaining_frames_to_provide, 0);
    int write_pos = frames_read;
    remaining_frames_to_provide -= frames_read;

    // Get the remaining audio frames from the producer using the callback.
    while (remaining_frames_to_provide > 0) {
        DCHECK_EQ(fifo_index_, fifo_->frames());
        fifo_index_ = 0;

        // Fill up the FIFO by acquiring audio data from the producer.
        read_cb_.Run(write_pos, fifo_.get());

        // Try to fulfill the request using what's available in the FIFO.
        frames_read = ReadFromFifo(destination, remaining_frames_to_provide, write_pos);
        write_pos += frames_read;
        remaining_frames_to_provide -= frames_read;
    }
}

void AudioPullFifo::Clear() { fifo_index_ = fifo_->frames(); }

int AudioPullFifo::SizeInFrames() const
{
    return fifo_->frames();
}

int AudioPullFifo::ReadFromFifo(AudioBus* destination,
    int frames_to_provide,
    int write_pos)
{
    int frames = std::min(frames_to_provide, fifo_->frames() - fifo_index_);
    if (frames <= 0)
        return 0;

    for (int ch = 0; ch < fifo_->channels(); ++ch) {
        const float* src = fifo_->channel(ch) + fifo_index_;
        float* dest = destination->channel(ch) + write_pos;
        memcpy(dest, src, frames * sizeof(*src));
    }

    fifo_index_ += frames;
    return frames;
}

} // namespace media
